Eye care professionals (ECPs), such as opticians, optometrists, opthalmologists, and eye doctors, typically dispense eye glasses to people based on a study of the person's vision that involves taking a medical history of the person's vision and a subjective refraction to get the person's prescription. After the person selects eyeglass frames, the ECP usually measures the centration of the frame for the person and orders lenses for the frame based on the person's prescription and the centration measurement.